1. Field of the Invention
The present invention concerns a fastening device for a diaphragm for x-ray radiation as well as a computed tomography apparatus having a radiation source with a diaphragm for x-ray radiation mounted on such a fastening device.
2. Description of the Prior Art
X-ray computed tomography apparatuses known from German OS 102 42 920 and German OS 102 44 898 have comprise a rotatable frame on which an x-ray source and an x-ray detector are disposed opposite one another. A patient bed on which the patient is positioned is moved through a patient opening of the rotary frame to acquire, for example, diagnostic x-ray images of a patient, with a number of x-ray projections of a body region of the patient being acquired from different projection directions. Slice images of the body region of the patient or volume representations can be reconstructed from the acquired x-ray projections of the body region.
In a diagnostic examination with an x-ray computed tomography apparatus, the patient is located on a patient bed in the patient opening of the rotary frame, or move through the patient opening. In order to alleviate feelings of spatial confinement as well as to enable more space for the medical personnel in the region of the patient opening for medical measures, as well as also to make it easier to examine particularly corpulent persons by means of x-ray computed tomography, there is a desire to enlarge the patient opening. The outer diameter of the rotating rotary frame, however, should not be enlarged. At the same time, the rotation speed of the rotary frame should be increased in order to develop new application fields for computed tomography, for example in cardiology. Both the enlargement of the patient opening and the increase of the rotation speed of the rotary frame require design changes to presently-used x-ray computed tomography apparatuses.
A known radiator diaphragm 1 associated with an x-ray source arranged on a rotary frame is shown in FIG. 1. Conventionally it is arranged with a filter unit 2 (separated by a non-load bearing intermediate plate 3) in a housing requiring a relatively large space. The housing 4 is conventionally fashioned from a several millimeter thick steel plate and, apart from openings for the passage of x-ray radiation, is provided with an x-ray-shielding material. The non-load bearing intermediate plate 3 that separates the filter unit 2 from the radiator diaphragm 1 is fastened in the supporting and scatter-radiation-sealed housing 4 with angle supports 5, as can be seen in the section view of FIG. 2. The massive housing 4 has not only a high space requirement on the rotary frame, which is disadvantageous with regard to the size of the patient opening, but also has a mass of several kilograms, which is also disadvantageous with regard to angular momentum on the rotary frame. High centrifugal forces must be accommodated by the fastening means with which the housing is fastened on the rotary frame.